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   1 /*
   2  *  net/dccp/ackvec.c
   3  *
   4  *  An implementation of the DCCP protocol
   5  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
   6  *
   7  *      This program is free software; you can redistribute it and/or modify it
   8  *      under the terms of the GNU General Public License as published by the
   9  *      Free Software Foundation; version 2 of the License;
  10  */
  11
  12 #include "ackvec.h"
  13 #include "dccp.h"
  14
  15 #include <linux/dccp.h>
  16 #include <linux/skbuff.h>
  17
  18 #include <net/sock.h>
  19
  20 int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
  21 {
  22         struct dccp_sock *dp = dccp_sk(sk);
  23         struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
  24         int len = av->dccpav_vec_len + 2;
  25         struct timeval now;
  26         u32 elapsed_time;
  27         unsigned char *to, *from;
  28
  29         dccp_timestamp(sk, &now);
  30         elapsed_time = timeval_delta(&now, &av->dccpav_time) / 10;
  31
  32         if (elapsed_time != 0)
  33                 dccp_insert_option_elapsed_time(sk, skb, elapsed_time);
  34
  35         if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
  36                 return -1;
  37
  38         /*
  39          * XXX: now we have just one ack vector sent record, so
  40          * we have to wait for it to be cleared.
  41          *
  42          * Of course this is not acceptable, but this is just for
  43          * basic testing now.
  44          */
  45         if (av->dccpav_ack_seqno != DCCP_MAX_SEQNO + 1)
  46                 return -1;
  47
  48         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
  49
  50         to    = skb_push(skb, len);
  51         *to++ = DCCPO_ACK_VECTOR_0;
  52         *to++ = len;
  53
  54         len  = av->dccpav_vec_len;
  55         from = av->dccpav_buf + av->dccpav_buf_head;
  56
  57         /* Check if buf_head wraps */
  58         if (av->dccpav_buf_head + len > av->dccpav_vec_len) {
  59                 const u32 tailsize = (av->dccpav_vec_len - av->dccpav_buf_head);
  60
  61                 memcpy(to, from, tailsize);
  62                 to   += tailsize;
  63                 len  -= tailsize;
  64                 from = av->dccpav_buf;
  65         }
  66
  67         memcpy(to, from, len);
  68         /*
  69          *      From draft-ietf-dccp-spec-11.txt:
  70          *
  71          *      For each acknowledgement it sends, the HC-Receiver will add an
  72          *      acknowledgement record.  ack_seqno will equal the HC-Receiver
  73          *      sequence number it used for the ack packet; ack_ptr will equal
  74          *      buf_head; ack_ackno will equal buf_ackno; and ack_nonce will
  75          *      equal buf_nonce.
  76          *
  77          * This implemention uses just one ack record for now.
  78          */
  79         av->dccpav_ack_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
  80         av->dccpav_ack_ptr   = av->dccpav_buf_head;
  81         av->dccpav_ack_ackno = av->dccpav_buf_ackno;
  82         av->dccpav_ack_nonce = av->dccpav_buf_nonce;
  83         av->dccpav_sent_len  = av->dccpav_vec_len;
  84
  85         dccp_pr_debug("%sACK Vector 0, len=%d, ack_seqno=%llu, "
  86                       "ack_ackno=%llu\n",
  87                       debug_prefix, av->dccpav_sent_len,
  88                       (unsigned long long)av->dccpav_ack_seqno,
  89                       (unsigned long long)av->dccpav_ack_ackno);
  90         return -1;
  91 }
  92
  93 struct dccp_ackvec *dccp_ackvec_alloc(const unsigned int len,
  94                                       const gfp_t priority)
  95 {
  96         struct dccp_ackvec *av = kmalloc(sizeof(*av) + len, priority);
  97
  98         if (av != NULL) {
  99                 av->dccpav_buf_len      = len;
 100                 av->dccpav_buf_head     =
 101                         av->dccpav_buf_tail = av->dccpav_buf_len - 1;
 102                 av->dccpav_buf_ackno    =
 103                         av->dccpav_ack_ackno = av->dccpav_ack_seqno = ~0LLU;
 104                 av->dccpav_buf_nonce = av->dccpav_buf_nonce = 0;
 105                 av->dccpav_ack_ptr      = 0;
 106                 av->dccpav_time.tv_sec  = 0;
 107                 av->dccpav_time.tv_usec = 0;
 108                 av->dccpav_sent_len     = av->dccpav_vec_len = 0;
 109         }
 110
 111         return av;
 112 }
 113
 114 void dccp_ackvec_free(struct dccp_ackvec *av)
 115 {
 116         kfree(av);
 117 }
 118
 119 static inline u8 dccp_ackvec_state(const struct dccp_ackvec *av,
 120                                    const unsigned int index)
 121 {
 122         return av->dccpav_buf[index] & DCCP_ACKVEC_STATE_MASK;
 123 }
 124
 125 static inline u8 dccp_ackvec_len(const struct dccp_ackvec *av,
 126                                  const unsigned int index)
 127 {
 128         return av->dccpav_buf[index] & DCCP_ACKVEC_LEN_MASK;
 129 }
 130
 131 /*
 132  * If several packets are missing, the HC-Receiver may prefer to enter multiple
 133  * bytes with run length 0, rather than a single byte with a larger run length;
 134  * this simplifies table updates if one of the missing packets arrives.
 135  */
 136 static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
 137                                                  const unsigned int packets,
 138                                                   const unsigned char state)
 139 {
 140         unsigned int gap;
 141         signed long new_head;
 142
 143         if (av->dccpav_vec_len + packets > av->dccpav_buf_len)
 144                 return -ENOBUFS;
 145
 146         gap      = packets - 1;
 147         new_head = av->dccpav_buf_head - packets;
 148
 149         if (new_head < 0) {
 150                 if (gap > 0) {
 151                         memset(av->dccpav_buf, DCCP_ACKVEC_STATE_NOT_RECEIVED,
 152                                gap + new_head + 1);
 153                         gap = -new_head;
 154                 }
 155                 new_head += av->dccpav_buf_len;
 156         }
 157
 158         av->dccpav_buf_head = new_head;
 159
 160         if (gap > 0)
 161                 memset(av->dccpav_buf + av->dccpav_buf_head + 1,
 162                        DCCP_ACKVEC_STATE_NOT_RECEIVED, gap);
 163
 164         av->dccpav_buf[av->dccpav_buf_head] = state;
 165         av->dccpav_vec_len += packets;
 166         return 0;
 167 }
 168
 169 /*
 170  * Implements the draft-ietf-dccp-spec-11.txt Appendix A
 171  */
 172 int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
 173                     const u64 ackno, const u8 state)
 174 {
 175         /*
 176          * Check at the right places if the buffer is full, if it is, tell the
 177          * caller to start dropping packets till the HC-Sender acks our ACK
 178          * vectors, when we will free up space in dccpav_buf.
 179          *
 180          * We may well decide to do buffer compression, etc, but for now lets
 181          * just drop.
 182          *
 183          * From Appendix A:
 184          *
 185          *      Of course, the circular buffer may overflow, either when the
 186          *      HC-Sender is sending data at a very high rate, when the
 187          *      HC-Receiver's acknowledgements are not reaching the HC-Sender,
 188          *      or when the HC-Sender is forgetting to acknowledge those acks
 189          *      (so the HC-Receiver is unable to clean up old state). In this
 190          *      case, the HC-Receiver should either compress the buffer (by
 191          *      increasing run lengths when possible), transfer its state to
 192          *      a larger buffer, or, as a last resort, drop all received
 193          *      packets, without processing them whatsoever, until its buffer
 194          *      shrinks again.
 195          */
 196
 197         /* See if this is the first ackno being inserted */
 198         if (av->dccpav_vec_len == 0) {
 199                 av->dccpav_buf[av->dccpav_buf_head] = state;
 200                 av->dccpav_vec_len = 1;
 201         } else if (after48(ackno, av->dccpav_buf_ackno)) {
 202                 const u64 delta = dccp_delta_seqno(av->dccpav_buf_ackno,
 203                                                    ackno);
 204
 205                 /*
 206                  * Look if the state of this packet is the same as the
 207                  * previous ackno and if so if we can bump the head len.
 208                  */
 209                 if (delta == 1 &&
 210                     dccp_ackvec_state(av, av->dccpav_buf_head) == state &&
 211                     (dccp_ackvec_len(av, av->dccpav_buf_head) <
 212                      DCCP_ACKVEC_LEN_MASK))
 213                         av->dccpav_buf[av->dccpav_buf_head]++;
 214                 else if (dccp_ackvec_set_buf_head_state(av, delta, state))
 215                         return -ENOBUFS;
 216         } else {
 217                 /*
 218                  * A.1.2.  Old Packets
 219                  *
 220                  *      When a packet with Sequence Number S arrives, and
 221                  *      S <= buf_ackno, the HC-Receiver will scan the table
 222                  *      for the byte corresponding to S. (Indexing structures
 223                  *      could reduce the complexity of this scan.)
 224                  */
 225                 u64 delta = dccp_delta_seqno(ackno, av->dccpav_buf_ackno);
 226                 unsigned int index = av->dccpav_buf_head;
 227
 228                 while (1) {
 229                         const u8 len = dccp_ackvec_len(av, index);
 230                         const u8 state = dccp_ackvec_state(av, index);
 231                         /*
 232                          * valid packets not yet in dccpav_buf have a reserved
 233                          * entry, with a len equal to 0.
 234                          */
 235                         if (state == DCCP_ACKVEC_STATE_NOT_RECEIVED &&
 236                             len == 0 && delta == 0) { /* Found our
 237                                                          reserved seat! */
 238                                 dccp_pr_debug("Found %llu reserved seat!\n",
 239                                               (unsigned long long)ackno);
 240                                 av->dccpav_buf[index] = state;
 241                                 goto out;
 242                         }
 243                         /* len == 0 means one packet */
 244                         if (delta < len + 1)
 245                                 goto out_duplicate;
 246
 247                         delta -= len + 1;
 248                         if (++index == av->dccpav_buf_len)
 249                                 index = 0;
 250                 }
 251         }
 252
 253         av->dccpav_buf_ackno = ackno;
 254         dccp_timestamp(sk, &av->dccpav_time);
 255 out:
 256         dccp_pr_debug("");
 257         return 0;
 258
 259 out_duplicate:
 260         /* Duplicate packet */
 261         dccp_pr_debug("Received a dup or already considered lost "
 262                       "packet: %llu\n", (unsigned long long)ackno);
 263         return -EILSEQ;
 264 }
 265
 266 #ifdef CONFIG_IP_DCCP_DEBUG
 267 void dccp_ackvector_print(const u64 ackno, const unsigned char *vector, int len)
 268 {
 269         if (!dccp_debug)
 270                 return;
 271
 272         printk("ACK vector len=%d, ackno=%llu |", len,
 273                (unsigned long long)ackno);
 274
 275         while (len--) {
 276                 const u8 state = (*vector & DCCP_ACKVEC_STATE_MASK) >> 6;
 277                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
 278
 279                 printk("%d,%d|", state, rl);
 280                 ++vector;
 281         }
 282
 283         printk("\n");
 284 }
 285
 286 void dccp_ackvec_print(const struct dccp_ackvec *av)
 287 {
 288         dccp_ackvector_print(av->dccpav_buf_ackno,
 289                              av->dccpav_buf + av->dccpav_buf_head,
 290                              av->dccpav_vec_len);
 291 }
 292 #endif
 293
 294 static void dccp_ackvec_trow_away_ack_record(struct dccp_ackvec *av)
 295 {
 296         /*
 297          * As we're keeping track of the ack vector size (dccpav_vec_len) and
 298          * the sent ack vector size (dccpav_sent_len) we don't need
 299          * dccpav_buf_tail at all, but keep this code here as in the future
 300          * we'll implement a vector of ack records, as suggested in
 301          * draft-ietf-dccp-spec-11.txt Appendix A. -acme
 302          */
 303 #if 0
 304         av->dccpav_buf_tail = av->dccpav_ack_ptr + 1;
 305         if (av->dccpav_buf_tail >= av->dccpav_vec_len)
 306                 av->dccpav_buf_tail -= av->dccpav_vec_len;
 307 #endif
 308         av->dccpav_vec_len -= av->dccpav_sent_len;
 309 }
 310
 311 void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
 312                                  const u64 ackno)
 313 {
 314         /* Check if we actually sent an ACK vector */
 315         if (av->dccpav_ack_seqno == DCCP_MAX_SEQNO + 1)
 316                 return;
 317
 318         if (ackno == av->dccpav_ack_seqno) {
 319 #ifdef CONFIG_IP_DCCP_DEBUG
 320                 struct dccp_sock *dp = dccp_sk(sk);
 321                 const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
 322                                         "CLIENT rx ack: " : "server rx ack: ";
 323 #endif
 324                 dccp_pr_debug("%sACK packet 0, len=%d, ack_seqno=%llu, "
 325                               "ack_ackno=%llu, ACKED!\n",
 326                               debug_prefix, 1,
 327                               (unsigned long long)av->dccpav_ack_seqno,
 328                               (unsigned long long)av->dccpav_ack_ackno);
 329                 dccp_ackvec_trow_away_ack_record(av);
 330                 av->dccpav_ack_seqno = DCCP_MAX_SEQNO + 1;
 331         }
 332 }
 333
 334 static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
 335                                             struct sock *sk, u64 ackno,
 336                                             const unsigned char len,
 337                                             const unsigned char *vector)
 338 {
 339         unsigned char i;
 340
 341         /* Check if we actually sent an ACK vector */
 342         if (av->dccpav_ack_seqno == DCCP_MAX_SEQNO + 1)
 343                 return;
 344         /*
 345          * We're in the receiver half connection, so if the received an ACK
 346          * vector ackno (e.g. 50) before dccpav_ack_seqno (e.g. 52), we're
 347          * not interested.
 348          *
 349          * Extra explanation with example:
 350          *
 351          * if we received an ACK vector with ackno 50, it can only be acking
 352          * 50, 49, 48, etc, not 52 (the seqno for the ACK vector we sent).
 353          */
 354         /* dccp_pr_debug("is %llu < %llu? ", ackno, av->dccpav_ack_seqno); */
 355         if (before48(ackno, av->dccpav_ack_seqno)) {
 356                 /* dccp_pr_debug_cat("yes\n"); */
 357                 return;
 358         }
 359         /* dccp_pr_debug_cat("no\n"); */
 360
 361         i = len;
 362         while (i--) {
 363                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
 364                 u64 ackno_end_rl;
 365
 366                 dccp_set_seqno(&ackno_end_rl, ackno - rl);
 367
 368                 /*
 369                  * dccp_pr_debug("is %llu <= %llu <= %llu? ", ackno_end_rl,
 370                  * av->dccpav_ack_seqno, ackno);
 371                  */
 372                 if (between48(av->dccpav_ack_seqno, ackno_end_rl, ackno)) {
 373                         const u8 state = (*vector &
 374                                           DCCP_ACKVEC_STATE_MASK) >> 6;
 375                         /* dccp_pr_debug_cat("yes\n"); */
 376
 377                         if (state != DCCP_ACKVEC_STATE_NOT_RECEIVED) {
 378 #ifdef CONFIG_IP_DCCP_DEBUG
 379                                 struct dccp_sock *dp = dccp_sk(sk);
 380                                 const char *debug_prefix =
 381                                         dp->dccps_role == DCCP_ROLE_CLIENT ?
 382                                         "CLIENT rx ack: " : "server rx ack: ";
 383 #endif
 384                                 dccp_pr_debug("%sACK vector 0, len=%d, "
 385                                               "ack_seqno=%llu, ack_ackno=%llu, "
 386                                               "ACKED!\n",
 387                                               debug_prefix, len,
 388                                               (unsigned long long)
 389                                               av->dccpav_ack_seqno,
 390                                               (unsigned long long)
 391                                               av->dccpav_ack_ackno);
 392                                 dccp_ackvec_trow_away_ack_record(av);
 393                         }
 394                         /*
 395                          * If dccpav_ack_seqno was not received, no problem
 396                          * we'll send another ACK vector.
 397                          */
 398                         av->dccpav_ack_seqno = DCCP_MAX_SEQNO + 1;
 399                         break;
 400                 }
 401                 /* dccp_pr_debug_cat("no\n"); */
 402
 403                 dccp_set_seqno(&ackno, ackno_end_rl - 1);
 404                 ++vector;
 405         }
 406 }
 407
 408 int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
 409                       const u8 opt, const u8 *value, const u8 len)
 410 {
 411         if (len > DCCP_MAX_ACKVEC_LEN)
 412                 return -1;
 413
 414         /* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */
 415         dccp_ackvec_check_rcv_ackvector(dccp_sk(sk)->dccps_hc_rx_ackvec, sk,
 416                                         DCCP_SKB_CB(skb)->dccpd_ack_seq,
 417                                         len, value);
 418         return 0;
 419 }